<template>
  <div
    :class="classes"
    v-click-outside.capture="onClickOutside"
    v-click-outside:mousedown.capture="onClickOutside"
  >
    <div v-if="$slots.prepend" :class="[prefixCls + '-group-prepend']">
      <slot name="prepend"></slot>
    </div>
    <div
      ref="reference"
      :class="selectionCls"
      :tabindex="selectTabindex"
      @blur="toggleHeaderFocus"
      @focus="toggleHeaderFocus"
      @click="toggleMenu"
      @keydown="handleKeydown"
      @mouseenter="hasMouseHoverHead = true"
      @mouseleave="hasMouseHoverHead = false"
    >
      <slot name="input">
        <input type="hidden" :name="name" :value="publicValue">
        <select-head
          :filterable="filterable"
          :multiple="multiple"
          :values="values"
          :clearable="canBeCleared"
          :disabled="selectDisabled"
          :remote="remote"
          :input-element-id="elementId"
          :initial-label="initialLabel"
          :placeholder="placeholder"
          :query-prop="query"
          @on-query-change="onQueryChange"
          @on-input-focus="isFocused = true"
          @on-input-blur="isFocused = false"
          @on-clear="clearSingleSelect"
        >
        </select-head>
      </slot>
    </div>
    <div v-if="$slots.append" :class="[prefixCls + '-group-append']">
      <slot name="append"></slot>
    </div>
    <transition name="transition-drop">
      <Drop
        ref="dropdown"
        v-transfer-dom
        :data-transfer="true"
        v-show="dropVisible"
        :visible="dropVisible"
        :class="dropdownCls"
        :prevElRect="dropPrevElRect()"
      >
        <ul v-show="showNotFoundLabel" :class="[prefixCls + '-not-found']"><li>{{ localeNotFoundText }}</li></ul>
        <ul
          :class="prefixCls + '-dropdown-list'"
        >
          <functional-options
            v-if="(!remote) || (remote && !loading)"
            :options="selectOptions"
            :slot-update-hook="updateSlotOptions"
            :slot-options="slotOptions"
          ></functional-options>
        </ul>
        <ul v-show="loading" :class="[prefixCls + '-loading']">{{ localeLoadingText }}</ul>
      </Drop>
    </transition>
  </div>
</template>
<script>
import Config from '../../config'
import Drop from './dropdown-select.vue'
import {directive as clickOutside} from 'v-click-outside-x'
import TransferDom from '../../directives/transfer-dom'
import { oneOf } from '../../utils/assist'
import { getBoundingClientRect, getToDocL, getToDocT, getWindowW, getWindowH, getDocScrollL, getDocScrollT } from '../../utils/position.js'
import Emitter from '../../mixins/emitter'
import Locale from '../../mixins/locale'
import SelectHead from './select-head.vue'
import FunctionalOptions from './functional-options.vue'
const prefixCls = `${Config.clsPrefix}select`
const localePrefix = `${Config.localePrefix}.select.`
const optionRegexp = /^d-option$|^Option$/i
const optionGroupRegexp = /option-?group/i
const findChild = (instance, checkFn) => {
  let match = checkFn(instance)
  if (match) return instance
  for (let i = 0, l = instance.$children.length; i < l; i++) {
    const child = instance.$children[i]
    match = findChild(child, checkFn)
    if (match) return match
  }
}
const findOptionsInVNode = (node) => {
  const opts = node.componentOptions
  if (opts && opts.tag.match(optionRegexp)) return [node]
  if (!node.children && (!opts || !opts.children)) return []
  const children = [...(node.children || []), ...((opts && opts.children) || [])]
  const options = children.reduce(
    (arr, el) => [...arr, ...findOptionsInVNode(el)], []
  ).filter(Boolean)
  return options.length > 0 ? options : []
}
const extractOptions = (options) => options.reduce((options, slotEntry) => {
  return options.concat(findOptionsInVNode(slotEntry))
}, [])
const applyProp = (node, propName, value) => {
  return {
    ...node,
    componentOptions: {
      ...node.componentOptions,
      propsData: {
        ...node.componentOptions.propsData,
        [propName]: value
      }
    }
  }
}
const getNestedProperty = (obj, path) => {
  const keys = path.split('.')
  return keys.reduce((o, key) => (o && o[key]) || null, obj)
}
const getOptionLabel = option => {
  if (option.componentOptions.propsData.label) return option.componentOptions.propsData.label
  const textContent = (option.componentOptions.children || []).reduce((str, child) => str + (child.text || ''), '')
  const innerHTML = getNestedProperty(option, 'data.domProps.innerHTML')
  return textContent || (typeof innerHTML === 'string' ? innerHTML : '')
}
const ANIMATION_TIMEOUT = 300
export default {
  name: `${Config.namePrefix}Select`,
  mixins: [ Emitter, Locale ],
  components: { FunctionalOptions, Drop, SelectHead },
  directives: { clickOutside, TransferDom },
  inject: {
    duiForm: {
      default: ''
    },
    duiFormItem: {
      default: ''
    }
  },
  provide () {
    return {
      'select': this
    }
  },
  props: {
    value: {
      type: [String, Number, Array],
      default: ''
    },
    // 使用时，也得设置 value 才行
    label: {
      type: [String, Number, Array],
      default: ''
    },
    multiple: {
      type: Boolean,
      default: false
    },
    disabled: {
      type: Boolean,
      default: false
    },
    clearable: {
      type: Boolean,
      default: false
    },
    placeholder: {
      type: String
    },
    filterable: {
      type: Boolean,
      default: false
    },
    filterMethod: {
      type: Function
    },
    remoteMethod: {
      type: Function
    },
    loading: {
      type: Boolean,
      default: false
    },
    loadingText: {
      type: String
    },
    size: {
      validator (value) {
        return oneOf(value, ['small', 'large', 'default'])
      },
      default () {
        return 'default'
      }
    },
    labelInValue: {
      type: Boolean,
      default: false
    },
    notFoundText: {
      type: String
    },
    placement: {
      validator (value) {
        return oneOf(value, ['top', 'bottom'])
      },
      default: 'bottom'
    },
    transfer: {
      type: Boolean,
      default: true
    },
    // Use for AutoComplete
    autoComplete: {
      type: Boolean,
      default: false
    },
    name: {
      type: String
    },
    elementId: {
      type: String
    }
  },
  mounted () {
    this.$on('on-select-selected', this.onOptionClick)
    // set the initial values if there are any
    if (!this.remote && this.selectOptions.length > 0) {
      this.values = this.getInitialValue().map(value => {
        if (typeof value !== 'number' && !value) return null
        return this.getOptionData(value)
      }).filter(Boolean)
    }
    this.checkUpdateStatus()
    this.dropDownRel = this.$refs.reference
  },
  data () {
    return {
      prefixCls: prefixCls,
      localePrefix: localePrefix,
      values: [],
      dropDownWidth: 0,
      visible: false,
      focusIndex: -1,
      isFocused: false,
      query: '',
      initialLabel: this.label,
      hasMouseHoverHead: false,
      slotOptions: this.$slots.default,
      caretPosition: -1,
      lastRemoteQuery: '',
      unchangedQuery: true,
      hasExpectedValue: false,
      preventRemoteCall: false,
      dropDownRel: null
    }
  },
  computed: {
    classes () {
      return [
        `${prefixCls}`,
        {
          [`${prefixCls}-group`]: (this.$slots.prepend || this.$slots.append),
          [`${prefixCls}-visible`]: this.visible,
          [`${prefixCls}-disabled`]: this.selectDisabled,
          [`${prefixCls}-multiple`]: this.multiple,
          [`${prefixCls}-single`]: !this.multiple,
          [`${prefixCls}-show-clear`]: this.showCloseIcon,
          [`${prefixCls}-${this.selectSize}`]: !!this.selectSize
        }
      ]
    },
    dropdownCls () {
      return {
        [prefixCls + '-dropdown-transfer']: this.transfer,
        [prefixCls + '-multiple']: this.multiple && this.transfer,
        [prefixCls + '-auto-complete']: this.autoComplete,
        [`${prefixCls}-dropdown-multiple`]: this.multiple,
        [`${prefixCls}-dropdown-single`]: !this.multiple
      }
    },
    selectionCls () {
      return {
        [`${prefixCls}-selection`]: !this.autoComplete,
        [`${prefixCls}-selection-focused`]: this.isFocused,
        [`${prefixCls}-selection-multiple`]: this.multiple,
        [`${prefixCls}-selection-single`]: !this.multiple
      }
    },
    queryStringMatchesSelectedOption () {
      const selectedOptions = this.values[0]
      if (!selectedOptions) return false
      const [query, label] = [this.query, selectedOptions.label].map(str => (str || '').trim())
      return !this.multiple && this.unchangedQuery && query === label
    },
    localeNotFoundText () {
      if (typeof this.notFoundText === 'undefined') {
        return this.t(localePrefix + 'noMatch')
      } else {
        return this.notFoundText
      }
    },
    localeLoadingText () {
      if (typeof this.loadingText === 'undefined') {
        return this.t(localePrefix + 'loading')
      } else {
        return this.loadingText
      }
    },
    transitionName () {
      return this.placement === 'bottom' ? 'slide-up' : 'slide-down'
    },
    dropVisible () {
      let status = true
      const noOptions = !this.selectOptions || this.selectOptions.length === 0
      if (!this.loading && this.remote && this.query === '' && noOptions) status = false
      if (this.autoComplete && noOptions) status = false
      return this.visible && status
    },
    showNotFoundLabel () {
      const {loading, remote, selectOptions} = this
      return selectOptions && selectOptions.length === 0 && (!remote || (remote && !loading))
    },
    publicValue () {
      if (this.labelInValue) {
        return this.multiple ? this.values : this.values[0]
      } else {
        return this.multiple ? this.values.map(option => option.value) : (this.values[0] || {}).value
      }
    },
    canBeCleared () {
      const uiStateMatch = this.hasMouseHoverHead || this.active
      const qualifiesForClear = !this.multiple && this.clearable
      return uiStateMatch && qualifiesForClear && this.reset // we return a function
    },
    selectOptions () {
      const selectOptions = []
      const slotOptions = (this.slotOptions || [])
      let optionCounter = -1
      const currentIndex = this.focusIndex
      const selectedValues = this.values.filter(Boolean).map(({value}) => value)
      if (this.autoComplete) {
        const copyChildren = (node, fn) => {
          return {
            ...node,
            children: (node.children || []).map(fn).map(child => copyChildren(child, fn))
          }
        }
        const autoCompleteOptions = extractOptions(slotOptions)
        const selectedSlotOption = autoCompleteOptions[currentIndex]
        return slotOptions.map(node => {
          if (node === selectedSlotOption || getNestedProperty(node, 'componentOptions.propsData.value') === this.value) return applyProp(node, 'isFocused', true)
          return copyChildren(node, (child) => {
            if (child !== selectedSlotOption) return child
            return applyProp(child, 'isFocused', true)
          })
        })
      }
      let hasDefaultSelected = slotOptions.some(option => this.query === option.key)
      for (let option of slotOptions) {
        const cOptions = option.componentOptions
        if (!cOptions) continue
        if (cOptions.tag.match(optionGroupRegexp)) {
          let children = cOptions.children
          // remove filtered children
          if (this.filterable) {
            children = children.filter(
              ({componentOptions}) => this.validateOption(componentOptions)
            )
          }
          cOptions.children = children.map(opt => {
            optionCounter = optionCounter + 1
            return this.processOption(opt, selectedValues, optionCounter === currentIndex)
          })
          // keep the group if it still has children
          if (cOptions.children.length > 0) selectOptions.push({...option})
        } else {
          // ignore option if not passing filter
          if (!hasDefaultSelected) {
            const optionPassesFilter = this.filterable ? this.validateOption(cOptions) : option
            if (!optionPassesFilter) continue
          }
          optionCounter = optionCounter + 1
          selectOptions.push(this.processOption(option, selectedValues, optionCounter === currentIndex))
        }
      }
      return selectOptions
    },
    flatOptions () {
      return extractOptions(this.selectOptions)
    },
    selectTabindex () {
      return this.selectDisabled || this.filterable ? -1 : 0
    },
    remote () {
      return typeof this.remoteMethod === 'function'
    },
    _duiFormItemSize () {
      return (this.duiFormItem || {}).duiFormItemSize
    },
    selectSize () {
      return this.size || this._duiFormItemSize || (this.$DUI || {}).size
    },
    selectDisabled () {
      return this.disabled || (this.duiForm || {}).disabled
    }
  },

  methods: {
    setQuery (query) { // PUBLIC API
      if (query) {
        this.onQueryChange(query)
        return
      }
      if (query === null) {
        this.onQueryChange('')
        this.values = []
      }
    },
    clearSingleSelect () { // PUBLIC API
      this.$emit('on-clear')
      this.hideMenu()
      if (this.clearable) this.reset()
    },
    getOptionData (value) {
      const option = this.flatOptions.find(({componentOptions}) => componentOptions.propsData.value === value)
      if (!option) return null
      const label = getOptionLabel(option)
      return {
        value: value,
        label: label
      }
    },
    getInitialValue () {
      const {multiple, remote, value} = this
      let initialValue = Array.isArray(value) ? value : [value]
      if (!multiple && (typeof initialValue[0] === 'undefined' || (String(initialValue[0]).trim() === '' && !Number.isFinite(initialValue[0])))) initialValue = []
      if (remote && !multiple && value) {
        const data = this.getOptionData(value)
        this.query = data ? data.label : String(value)
      }
      return initialValue.filter((item) => {
        return Boolean(item) || item === 0
      })
    },
    processOption (option, values, isFocused) {
      if (!option.componentOptions) return option
      const optionValue = option.componentOptions.propsData.value
      const disabled = option.componentOptions.propsData.disabled
      const isSelected = values.includes(optionValue)
      const propsData = {
        ...option.componentOptions.propsData,
        selected: isSelected,
        isFocused: isFocused,
        disabled: typeof disabled === 'undefined' ? false : disabled !== false
      }
      return {
        ...option,
        componentOptions: {
          ...option.componentOptions,
          propsData: propsData
        }
      }
    },
    validateOption ({children, elm, propsData}) {
      if (this.queryStringMatchesSelectedOption) return true
      const value = propsData.value
      const label = propsData.label || ''
      const textContent = (elm && elm.textContent) || (children || []).reduce((str, node) => {
        const nodeText = node.elm ? node.elm.textContent : node.text
        return `${str} ${nodeText}`
      }, '') || ''
      const stringValues = JSON.stringify([value, label, textContent])
      const query = this.query.toLowerCase().trim()
      return stringValues.toLowerCase().includes(query)
    },
    toggleMenu (e, force) {
      if (this.selectDisabled) {
        return false
      }
      this.visible = typeof force !== 'undefined' ? force : !this.visible
      if (this.visible) {
        this.dropDownWidth = this.$el.getBoundingClientRect().width
        this.broadcast('Drop', 'on-update-popper')
      }
    },
    hideMenu () {
      this.toggleMenu(null, false)
      setTimeout(function () { this.unchangedQuery = true }, ANIMATION_TIMEOUT)
    },
    onClickOutside (event) {
      if (this.visible) {
        if (event.type === 'mousedown') {
          event.preventDefault()
          return
        }
        if (this.transfer) {
          const {$el} = this.$refs.dropdown
          if ($el === event.target || $el.contains(event.target)) {
            return
          }
        }
        if (this.filterable) {
          const input = this.$el.querySelector('input[type="text"]')
          this.caretPosition = input.selectionStart
          this.$nextTick(() => {
            const caretPosition = this.caretPosition === -1 ? input.value.length : this.caretPosition
            input.setSelectionRange(caretPosition, caretPosition)
          })
        }
        if (!this.autoComplete) event.stopPropagation()
        event.preventDefault()
        this.hideMenu()
        this.isFocused = true
      } else {
        this.caretPosition = -1
        this.isFocused = false
      }
    },
    reset () {
      this.query = ''
      this.focusIndex = -1
      this.unchangedQuery = true
      this.values = []
    },
    handleKeydown (e) {
      if (!oneOf(e.key, ['Tab', 'Escape', 'Enter', 'ArrowUp', 'ArrowDown'])) return
      if (this.visible) {
        e.preventDefault()
        if (e.key === 'Tab') {
          e.stopPropagation()
        }
        // Esc slide-up
        if (e.key === 'Escape') {
          e.stopPropagation()
          this.hideMenu()
        }
        // next
        if (e.key === 'ArrowUp') {
          this.navigateOptions(-1)
        }
        // prev
        if (e.key === 'ArrowDown') {
          this.navigateOptions(1)
        }
        // enter
        if (e.key === 'Enter') {
          if (this.focusIndex === -1) return this.hideMenu()
          const optionComponent = this.flatOptions[this.focusIndex]
          const option = this.getOptionData(optionComponent.componentOptions.propsData.value)
          this.onOptionClick(option)
        }
      } else {
        const keysThatCanOpenSelect = ['ArrowUp', 'ArrowDown']
        if (keysThatCanOpenSelect.includes(e.key)) this.toggleMenu(null, true)
      }
    },
    navigateOptions (direction) {
      const optionsLength = this.flatOptions.length - 1
      let index = this.focusIndex + direction
      if (index < 0) index = optionsLength
      if (index > optionsLength) index = 0
      // find nearest option in case of disabled options in between
      if (direction > 0) {
        let nearestActiveOption = -1
        for (let i = 0; i < this.flatOptions.length; i++) {
          const optionIsActive = !this.flatOptions[i].componentOptions.propsData.disabled
          if (optionIsActive) nearestActiveOption = i
          if (nearestActiveOption >= index) break
        }
        index = nearestActiveOption
      } else {
        let nearestActiveOption = this.flatOptions.length
        for (let i = optionsLength; i >= 0; i--) {
          const optionIsActive = !this.flatOptions[i].componentOptions.propsData.disabled
          if (optionIsActive) nearestActiveOption = i
          if (nearestActiveOption <= index) break
        }
        index = nearestActiveOption
      }
      this.focusIndex = index
    },
    onOptionClick (option) {
      if (this.multiple) {
        // keep the query for remote select
        if (this.remote) this.lastRemoteQuery = this.lastRemoteQuery || this.query
        else this.lastRemoteQuery = ''

        const valueIsSelected = this.values.find(({value}) => value === option.value)
        if (valueIsSelected) {
          this.values = this.values.filter(({value}) => value !== option.value)
        } else {
          this.values = this.values.concat(option)
        }

        this.isFocused = true // so we put back focus after clicking with mouse on option elements
      } else {
        this.query = String(option.label).trim()
        this.values = [option]
        this.lastRemoteQuery = ''
        this.hideMenu()
      }
      this.focusIndex = this.flatOptions.findIndex((opt) => {
        if (!opt || !opt.componentOptions) return false
        return opt.componentOptions.propsData.value === option.value
      })
      if (this.filterable) {
        const inputField = this.$el.querySelector('input[type="text"]')
        if (!this.autoComplete) this.$nextTick(() => inputField.focus())
      }
      this.broadcast('Drop', 'on-update-popper')
    },
    onQueryChange (query) {
      if (query.length > 0 && query !== this.query) this.visible = true
      this.query = query
      this.unchangedQuery = this.visible
    },
    toggleHeaderFocus ({type}) {
      if (this.selectDisabled) {
        return
      }
      this.isFocused = type === 'focus'
    },
    updateSlotOptions () {
      this.slotOptions = this.$slots.default
    },
    checkUpdateStatus () {
      if (this.getInitialValue().length > 0 && this.selectOptions.length === 0) {
        this.hasExpectedValue = true
      }
    },
    dropPrevElRect () {
      let prevEl = this.dropDownRel
      let obj = {}
      if (prevEl) {
        obj.boundingRect = getBoundingClientRect(prevEl)
        obj.toDocTop = getToDocT(prevEl)
        obj.toDocLeft = getToDocL(prevEl)
        obj.windowW = getWindowW()
        obj.windowH = getWindowH()
        obj.scrollLeft = getDocScrollL()
        obj.scrollTop = getDocScrollT()
      }
      return obj
    }
  },
  watch: {
    value (value) {
      const {getInitialValue, getOptionData, publicValue} = this
      this.checkUpdateStatus()
      if (value === '') this.values = []
      else if (JSON.stringify(value) !== JSON.stringify(publicValue)) {
        this.$nextTick(function () { this.values = getInitialValue().map(getOptionData).filter(Boolean) })
      }
    },
    values (now, before) {
      const newValue = JSON.stringify(now)
      const oldValue = JSON.stringify(before)
      // v-model is always just the value, event with labelInValue === true
      const vModelValue = (this.publicValue && this.labelInValue)
        ? (this.multiple
          ? this.publicValue.map(({value}) => value)
          : this.publicValue.value)
        : this.publicValue
      const shouldEmitInput = newValue !== oldValue && vModelValue !== this.value
      if (shouldEmitInput) {
        this.$emit('input', vModelValue) // to update v-model
        this.$emit('on-change', this.publicValue)
        this.dispatch(`${Config.namePrefix}FormItem`, 'on-form-change', this.publicValue)
      }
    },
    query (query) {
      this.$emit('on-query-change', query)
      const {remoteMethod, lastRemoteQuery} = this
      const hasValidQuery = query !== '' && (query !== lastRemoteQuery || !lastRemoteQuery)
      const shouldCallRemoteMethod = remoteMethod && hasValidQuery && !this.preventRemoteCall
      this.preventRemoteCall = false // remove the flag
      if (shouldCallRemoteMethod) {
        this.focusIndex = -1
        const promise = this.remoteMethod(query)
        this.initialLabel = ''
        if (promise && promise.then) {
          promise.then(options => {
            if (options) this.options = options
          })
        }
      }
      if (query !== '' && this.remote) this.lastRemoteQuery = query
    },
    loading (state) {
      if (state === false) {
        this.updateSlotOptions()
      }
    },
    isFocused (focused) {
      const el = this.filterable ? this.$el.querySelector('input[type="text"]') : this.$el
      el[this.isFocused ? 'focus' : 'blur']()
      // restore query value in filterable single selects
      const [selectedOption] = this.values
      if (selectedOption && this.filterable && !this.multiple && !focused) {
        const selectedLabel = String(selectedOption.label || selectedOption.value).trim()
        if (selectedLabel && this.query !== selectedLabel) {
          this.preventRemoteCall = true
          this.query = selectedLabel
        }
      }
    },
    focusIndex (index) {
      if (index < 0 || this.autoComplete) return
      // update scroll
      const optionValue = this.flatOptions[index].componentOptions.propsData.value
      const optionInstance = findChild(this, ({$options}) => {
        return $options.componentName === 'select-item' && $options.propsData.value === optionValue
      })
      let bottomOverflowDistance = optionInstance.$el.getBoundingClientRect().bottom - this.$refs.dropdown.$el.getBoundingClientRect().bottom
      let topOverflowDistance = optionInstance.$el.getBoundingClientRect().top - this.$refs.dropdown.$el.getBoundingClientRect().top
      if (bottomOverflowDistance > 0) {
        this.$refs.dropdown.$el.scrollTop += bottomOverflowDistance
      }
      if (topOverflowDistance < 0) {
        this.$refs.dropdown.$el.scrollTop += topOverflowDistance
      }
    },
    dropVisible (open) {
      this.broadcast('Drop', open ? 'on-update-popper' : 'on-destroy-popper')
    },
    selectOptions () {
      if (this.hasExpectedValue && this.selectOptions.length > 0) {
        if (this.values.length === 0) {
          this.values = this.getInitialValue()
        }
        this.values = this.values.map(this.getOptionData).filter(Boolean)
        this.hasExpectedValue = false
      }

      if (this.slotOptions && this.slotOptions.length === 0) {
        this.query = ''
      }
    },
    visible (state) {
      this.$emit('on-open-change', state)
    }
  }
}
</script>
